Method and System for Demonstrating Discrepancies in Speedometers in Vehicles

ABSTRACT

The invention relates to a method and a system to demonstrate discrepancies in the speedometer of a vehicle. In a preferred embodiment, the method and the system further comprise the possibility of adjusting or calibrating the speedometer with the use of demonstrated discrepancies automatically or after approval by the user. The speed of the vehicle is measured with an external measuring device and the information about the speed is sent to a receiver in the vehicle. By comparing received information about speed with information of speed according to the speedometer of the vehicle information about possible discrepancies is made available to a user.

The present invention relates to a method and a system for showing discrepancies in speedometers in vehicles.

A number of methods, systems and procedures to calibrate or adjust speedometers in vehicles, for example cars, are known. One way to adjust a speedometer is to place the car on rollers that are connected to a measuring apparatus, whereupon the speedometer can be adjusted according to the measurement. This control is often used if the speedometer is destroyed or there is a suspicion of a large discrepancy.

However, most cars have a discrepancy where the speedometer is adjusted down. This means, for example, that the real speed of the car can be 95 km/h when the speedometer indicates 100 km/h. This is done deliberately by car manufacturers to avoid claims for compensation from drivers that are fined because of speedometers being adjusted too high.

The discrepancy will only be larger when the tires of the car are worn. When the profile in a tire with a diameter of 60 cm is worn by 3 mm, the circumference becomes 18.8 mm smaller. At a speed of 100 km/h, this means a discrepancy of about 1 km/h. A speedometer of a car with a standard discrepancy of 5 km/h and rather worn tires will therefore indicate that the speed of the car is 94 km/h.

Cars with excessive discrepancies in the speedometer can cause dangerous traffic situations. For example, it can be irritating for someone driving behind a car that drives too slowly, something that can lead to dangerous overtaking situations.

Another disadvantage with this is that one can feel that the speed limit on the actual stretch of road is too low in relation to, for example, the width of the road, number of lanes, bends, vegetation by the side of the road, and other factors that influence the driver's feeling for speed. The driver will not risk speeding fines and sticks to the speed limit, at least according to the speedometer, while he/she would, in reality, be a more relaxed driver if the speed had been a few kilometres per hour higher. In reality, the driver could be able to drive a little bit faster without breaking the speed limit. With a speedometer with too a large discrepancy, the driver goes slower than what is felt to be natural, and must therefore look at the speedometer all the time, something that takes his attention from the road and the traffic. This can clearly lead to dangerous situations.

For the last disadvantage, there are systems that can be set at a certain speed. Some systems, such as automatic speed controllers or cruise control systems; keep the car at a given speed, until the driver brakes or accelerates. Other systems emit a signal when a predetermined maximum speed is exceeded, for example, a voice signal, sound signal or light signal. However, such systems contribute to a certain degree only, as all such systems that the present inventor is aware of use the speed measuring device of the car as a basis.

Claim 28 of U.S. Pat. No. 6,353,796 B1 describes a device for calibration of a speedometer or a distance measuring system of a vehicle. The system estimates a driven distance with the use of, for example, GPS (Global Positioning System), GLONASS (Global Navigation Satellite System) or LORAN (Long Range Navigation), which estimate the distance used to calculate an estimated speed of a vehicle, which in turn can be used to calibrate the speedometer. The problem with this and similar systems is that they are complex and expensive, that it requires at least two, but preferably many, points where the measuring takes place to be able to calculate an estimated speed that is sufficiently accurate to be useful.

It is the intention to solve the above mentioned problems with the present invention.

The method and the system according to the present invention are characterised by the characteristic parts of the main claims 1 and 7.

Alternative embodiments are described in the dependent claims.

A preferred embodiment of the system shall now be described with the help of the enclosed FIG. 1.

The FIGURE shows schematically a speed measuring device 10 that can be a radar measuring point. The speed measuring device measures the speed of, for example, a car at 94 km/h, and sends this information to a receiver 20 in the car. The measurement is further sent to a comparator device 40. The speedometer 30 of the car measures a speed of 99 km/h, and sends this information to the comparator device 40 also. In the comparator device, it is calculated that the difference between the externally measured speed and the speed measured by the speedometer in the car is +5 km/h, ergo, the speedometer of the car indicates 5 km/h more that the real speed. The discrepancy is made known to the driver with the help of a screen 50. A question of whether the driver wishes to adjust the speedometer of the car to the correct speed or not can come up on the screen. If the driver chooses to adjust the speedometer, the comparator device 40, or any other digital or analogue adjustment unit, dependent on whether the speedometer is digital or analogue, adjusts the speedometer, possibly with a set discrepancy upwards to still have a small safety margin, which is, however, smaller than the measured and calculated discrepancy. In the example shown, the speedometer is adjusted down from 99 km/h by 5×0.95 km/h, i.e. to 94.25 km/h, while the real speed is 94 km/h. This means that the discrepancy of the speedometer is corrected from +5.3% to +0.27%.

For the speed measuring device 10 to be able to transmit speed information to the correct car, it can be advantageous that every car is given a unique ID, such as a reference number. This ID can be transmitted from the speed measuring device 10 to the receiver 20 in the car just before, during or just after the speed measurement, and can be stored temporarily in the speed measuring device and/or the car's receiver. Another variant is a measuring point (electronic loop) in the road that sends out an ID to the speed measuring device and to the car's receiver. When the speed measuring device has completed the task of measuring the respective vehicle, speed information is sent together with associated ID from the speed measuring device 10 to the receiver 20 in the vehicle. The vehicle can then carry out a comparison of its ID with the received ID and if there is an agreement, the speed comparison is as described above. If there is no agreement, no calculation of discrepancy is carried out.

In most cars, there is a connection between speedometer and the trip counter. When the discrepancy of the speedometer is on the average 5%, the total distance driven for the car will consequently deviate by 5%. When one shall sell a used car, this discrepancy will mean 5000 km per 100 000 km. Thus one can cross psychologically important borders at the sale of a car. A car that shows it has done 97 000 km will be sold easier than a car that shows it has done 102 000 km.

In an alternative embodiment of the invention, it can be put in when the tires of the car are changed, and also possibly the dimensions of the tires and the depth of the profile. The system can, using two or more discrepancy determinations calculated over a given one or more time periods, calculate when the profile of the tires begins to be worn, and warn the driver about this.

The user can preferably set in a value, where all received discrepancies below this value are not repeated to the user. This is to avoid unnecessarily disturbing the user when driving.

Furthermore, it can be set in that the user does not get information about any possible discrepancies before she/he stops the car. It can then be displayed after stopping the vehicle, when and where the receiver received a measured value and then the user can choose whether the speedometer shall be adjusted according to the estimated discrepancy.

In another preferred system, the driver of the vehicle will not get information about calculated discrepancy, but this will be checked by a car mechanic every time the car is being serviced. A double check can then be carried out at the garage, for example, with the help of a roller bench.

If the user has adjusted the speedometer as the car tires get worn, this must be inserted in the system when new tires are being fitted, so that the system can calculate a new value for the correct speed, or so that the system can zero the settings of the speedometer to the values when delivered from the factory.

It must be emphasised that a system according to the present invention should preferably be approved by the authorities in different countries or regions. Permanent measuring points along the road, for example radar points, should be calibrated accurately for the system to function well. It may be that measuring points that send information to the car at the same time send information on when it was calibrated, by which department, possibly with how many percent accuracy it measures, possibly a kind of digital signature to authenticate that it is an approved calibration point, or other information that can contribute to the system functioning as reliably and accurately as possible. 

1. Method for demonstrating discrepancies in speedometers in vehicles, comprising the steps: a) measuring the speed of the vehicle with an external measuring device, b) sending information about speed from the external measuring device to a receiver in the vehicle: c) comparing the information of speed received from the external measuring device with information of speed according to the speedometer of the vehicle; d) making the information about possible discrepancies available to a user.
 2. Method according to claim 1, characterised in that the vehicle is chosen from a group comprising cars, motorbikes, mopeds, boats and the like.
 3. Method according to claim 1, characterised in that the user of the system is the driver of the vehicle, or a person skilled in the arts that can carry out the service of the vehicle.
 4. Method according to claim 1, characterised in that the information about possible discrepancies is made available by information on a screen, a mechanical pointer, a measuring clock, or other known devices.
 5. Method according to claim 1, characterised in that it further comprises the following step: adjusting the speedometer of the vehicle with the use of information about discrepancy, where the adjustment can be carried out automatically or after approval by the user.
 6. Method according to claim 1, characterised in that the information about discrepancy is used to calculate wear on the tire of a car, motorbike, moped or other vehicle with tires by comparing the discrepancy of the speedometer periodically.
 7. System for demonstrating discrepancies in speedometers of vehicles, characterised in that the system comprises: a) an external device for the measuring of the speed of a vehicle; b) a transmitter to send information about speed from the external device to a receiver in the vehicle; c) a device to compare the received information about speed with information about speed according to the speedometer of the vehicle; and d) a device to make information about possible discrepancies available to a user.
 8. System according to claim 7, characterised in that the device in subparagraph d) is a screen, a mechanical pointer, a measuring clock, or an other known device.
 9. System according to claim 7, characterised in that it further comprises a device for adjusting the speedometer of the vehicle by the use of information about the discrepancy, where the adjustment can be carried out automatically or after approval by the user.
 10. System according to claim 7, characterised in that the system is arranged in a car, where the operating appliances are built into a panel in the middle of the steering wheel, and where the panel is arranged stationary with respect to the dashboard so that the panel does not alter its position when the steering wheel is turned.
 11. System according to claim 10, characterised in that the panel further comprises a screen to show information about the operation and setting of the system, where the screen can be of the touch-screen type, where the operating buttons of the system constitute icons on the screen.
 12. System according to claim 8, characterised in that it further comprises a device for adjusting the speedometer of the vehicle by the use of information about the discrepancy, where the adjustment can be carried out automatically or after approval by the user.
 13. System according to claim 8, characterised in that the system is arranged in a car, where the operating appliances are built into a panel in the middle of the steering wheel, and where the panel is arranged stationary with respect to the dashboard so that the panel does not alter its position when the steering wheel is turned.
 14. System according to claim 9, characterised in that the system is arranged in a car, where the operating appliances are built into a panel in the middle of the steering wheel, and where the panel is arranged stationary with respect to the dashboard so that the panel does not alter its position when the steering wheel is turned.
 15. A method for demonstrating discrepancies in speedometers in vehicles, where the speed according to vehicle speedometer is compared with the vehicle speed information from a second measuring device, for optionally adjusting the vehicle speedometer to a corrected speed based on the measured speed discrepancies, comprising the steps: a) measuring the speed of the vehicle with an external measuring device, b) continuously sending said measured information about speed from the external measuring device to a receiver in the vehicle, c) comparing said information of speed received from the external measuring device with the information of speed according to the speedometer of the vehicle, d) making available said information about possible speed discrepancies to the vehicle user, and adjusting the speedometer adjustment automatically or by approval by the user, and e) using the information about discrepancy to calculate wear on the tires of a car, motorbike, moped or other vehicle by comparing the discrepancy of the speedometer.
 16. A method according to claim 15 wherein said external measuring device is a radar device.
 17. A method according to claim 15, comprising adjusting the speedometer, with a set speed discrepancy upwards to still have a safety margin, which is smaller than the measured and calculated discrepancy.
 18. A method according to claim 15, comprising making available the information about any of said discrepancies by information on a screen, a mechanical pointer, a measuring clock, or other known devices.
 19. A method according to claim 15, comprising carrying out the calculation of said discrepancy only when an unique ID, such as a reference number, of the vehicle, agrees with an ID transmitted from the measuring device.
 20. A method according to claim 19, comprising transmitting of said ID from the speed measuring device to the vehicle receiver just before, during or after the speed measurement, and temporarily storing of said ID in the speed measuring device and/or the receiver of the vehicle.
 21. A method according to claim 19, comprising emitting said ID from a measuring point (electronic loop) in the road to the speed measuring device and to the vehicle receiver, and when the speed measuring device has completed measuring the respective vehicle, sending the speed information together with associated ID from the speed measuring device to the vehicle receiver, and then the receiver makes a comparison of its ID with the received ID and if there is an agreement, carrying out the speed comparison, and if there is no agreement, no calculation of discrepancy is carried out.
 22. A method according to claim 15 where said vehicles comprise cars, motorbikes, mopeds and boats.
 23. A system for demonstrating discrepancies in speedometer of a vehicle, comprising a second vehicle speed measuring device, and a comparator unit for calculating any speed discrepancies between the speedometer and said second vehicle speed measuring device, for optionally adjusting the vehicle speedometer to a corrected speed based on the measured speed discrepancies, characterised in that: a) said second vehicle speed measuring device comprises an external device, including a transmitter to send information about speed from the external device to a receiver in the vehicle, and b) the system includes a device to make information about possible discrepancies available to a user.
 24. A method according to claim 23, wherein said external device is a radar device.
 25. A system according to claim 23, characterised in that the information about any of said discrepancies is made available by information on a screen, a mechanical pointer, a measuring clock, or other known devices.
 26. A system according to claim 23, characterised in that the operating appliances of the system are built into a panel in the middle of the steering wheel of a car, and where the panel is stationary with respect to the dashboard so that the panel does not alter its position when the steering wheel is turned.
 27. A system according to claim 26, characterised in that the panel further comprises a screen to show information about the operation and setting of the system.
 28. A method according to claim 27, where said screen is the touch-screen type, where the operating buttons of the system constitute icons on the screen. 